更快的％in％运算符 [英] Faster %in% operator

问题描述

fastmatch 软件包为重复匹配实现了match的更快版本(例如循环):

The fastmatch package implements a much faster version of match for repeated matches (e.g. in a loop):

set.seed(1)
library(fastmatch)
table <- 1L:100000L
x <- sample(table, 10000, replace=TRUE)
system.time(for(i in 1:100) a <-  match(x, table))
system.time(for(i in 1:100) b <- fmatch(x, table))
identical(a, b)

%in%是否有类似的实现方式，可以用来加快重复查找的速度?

Is there a similar implementation for %in% I could use to speed up repeated lookups?

推荐答案

查看%in%的定义:

R> `%in%`
function (x, table) 
match(x, table, nomatch = 0L) > 0L
<bytecode: 0x1fab7a8>
<environment: namespace:base>

编写自己的%fin%函数很容易:

It's easy to write your own %fin% function:

`%fin%` <- function(x, table) {
  stopifnot(require(fastmatch))
  fmatch(x, table, nomatch = 0L) > 0L
}
system.time(for(i in 1:100) a <- x %in% table)
#    user  system elapsed 
#   1.780   0.000   1.782 
system.time(for(i in 1:100) b <- x %fin% table)
#    user  system elapsed 
#   0.052   0.000   0.054
identical(a, b)
# [1] TRUE

这篇关于更快的％in％运算符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！